Polishing device and polishing method

ABSTRACT

A polishing device according to the present invention includes: a plurality of workpiece holding units that respectively hold workpieces; a base part that is rotatable about a center axis, and is arranged such that the plurality of workpiece holding units are arranged mutually at an equal interval on an identical circumference at an arbitrary distance from the center axis; and a plurality of workpiece polishing units that polish polishing target surfaces of the workpieces held by the workpiece holding units, the base part rotates in one direction about the center axis to sequentially move the workpiece holding units that hold the workpieces to the plurality of polishing positions such that the plurality of workpiece polishing units polish the workpieces, and moves the workpieces polished by the plurality of workpiece polishing units to the workpiece exchange position, and exchanges the polished workpieces with a workpiece that is not yet polished.

FIELD OF THE INVENTION

The present invention relates to a polishing device and a polishing method for polishing workpieces such as optical lenses.

BACKGROUND OF THE INVENTION

As disclosed in, for example, JP 56-089447 U, a conventional polishing device for optical lenses and the like performs polishing by rotating a lower shaft at a fixed position, moving a knockout bar on an upper end surface of the lower shaft, and causing relative movement of a machining target lens and a blade between the lower shaft and the knockout bar.

Furthermore, as disclosed in JP 2000-108002 A, there is a device that distributes electricity to a polishing liquid in which charged fine abrasive grains are dispersed, adhere the fine abrasive grains to a polishing tool that has an opposite polarity to that of the fine abrasive grains, and polishing a lens surface by the polishing tool.

However, these polishing devices have difficulty in performing polishing while changing polishing conditions for a polishing area of a polishing target surface of a machining target lens (e.g., a surrounding part of a machining target lens and the like). Furthermore, although it is conceived to perform polishing by changing a polishing tool per polishing area, these polishing devices have a problem that it takes time to change a polishing tool, therefore a machining (polishing) time becomes longer and, as a result, operability and manufacturing efficiency lower.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a polishing device and a polishing method that can accurately polish workpieces while flexibly meeting various outer shape specifications and improving production and operability.

In order to solve the above-mentioned problems, the polishing device according to the present invention is a polishing device that polishes a workpiece, the polishing device comprising: a plurality of workpiece holding units that respectively hold the workpieces; a base part that is rotatable about a center axis, and is arranged such that the plurality of workpiece holding units are arranged mutually at an equal interval on an identical circumference at an arbitrary distance from the center axis; and a plurality of workpiece polishing units that polish polishing target surfaces of the workpieces held by the workpiece holding units, wherein the plurality of workpiece polishing units are provided above the base part and at a plurality of polishing positions for polishing the workpieces, and are not provided at a workpiece exchange position for exchanging the polished workpieces held by the workpiece holding units, the plurality of polishing positions and the workpiece exchange position are provided on an identical circumference about the center axis of the base part, and the base part rotates in one direction about the center axis to sequentially move the workpiece holding units that hold the workpieces to the plurality of polishing positions such that the plurality of workpiece polishing units polish the workpieces, and moves the workpieces polished by the plurality of workpiece polishing units to the workpiece exchange position, and exchanges the polished workpieces with a workpiece that is not yet polished.

According to the above configuration, the plurality of polishing positions and the workpiece exchange position are provided above the base part and on the same circumference about the center axis of the base part. Furthermore, the plurality of workpiece polishing units are provided to meet the respective polishing positions. Furthermore, the plurality of workpiece holding units are arranged above the base part, and mutually at the equal interval on the identical circumference at the arbitrary distance from the center axis of the base part. Hence, by rotating the base part in one direction about the center axis, it is possible to sequentially move the workpiece holding units that hold the workpieces to the plurality of polishing positions. Furthermore, it is possible to move the workpiece holding units that hold the polished workpieces at each polishing position to the workpiece exchange position.

Consequently, according to the above configuration, it is possible to change a polishing area or polish conditions of the workpiece at each polishing position by, for example, changing each workpiece polishing unit. As a result, it is possible to manufacture an accurate workpiece to flexibly meet various outer shape specifications. Furthermore, the workpiece polishing unit is not provided at the workpiece exchange position, so that it is possible to easily exchange the polished workpiece with the workpiece that is not yet polished while polishing each workpiece at each polishing position. As a result, the polishing device according to the above configuration can improve productivity compared to a conventional polishing device.

In the configuration described above, it is preferable that the workpiece holding units are attachably and detachably provided on the base part. Consequently, compared to a case where the workpiece holding units are fixed onto the base part, it is possible to more easily exchange the workpiece at the workpiece exchange position, and further improve productivity.

In the configuration described above, it is preferable that the polishing device comprises a plurality of driven pulleys that are provided to the base part and are respectively provided to meet the plurality of workpiece holding units; an endless belt that is wound around all driven pulleys at positions meeting the polishing positions among the plurality of drive pulleys, or an outer circumference of the base part; and a driving pulley that is coupled to all the driven pulleys at the positions meeting the polishing positions or the base part with the endless belt interposed therebetween. According to this configuration, when the driving pulley rotates and drives, it is possible to rotate the plurality of driven pulleys coupled to the driving pulley with the endless belt interposed therebetween. In this regard, the plurality of driven pulleys are provided to the base part to respectively meet the plurality of workpiece holding units, and are located at the polishing positions. Consequently, it is possible to rotate the base part itself by rotating the driven pulleys. Furthermore, it is possible to rotate the base part by winding the endless belt around the outer circumference of the base part, too. Furthermore, by rotating the base part, it is possible to sequentially move the workpiece holding units that hold the workpieces to the plurality of polishing positions. Furthermore, it is possible to move the workpiece holding units that hold the polished workpieces at each polishing position to the workpiece exchange position.

In order to solve the above-mentioned problems, the polishing method according to the present invention is a polishing method for polishing the workpiece by using the polishing device, the polishing method comprising: causing the plurality of workpiece holding units to respectively hold the workpieces, the plurality of workpiece holding units being arranged mutually at an equal interval on an identical circumference at an arbitrary distance from the center axis of the base part; rotating the base part in one direction about the center axis to sequentially move the workpiece holding units that hold the workpieces to the plurality of polishing positions such that the plurality of workpiece polishing units polish the workpieces; and moving the workpieces to the workpiece exchange position, and exchanging the polished workpieces with a workpiece that is not yet polished.

According to the above configuration, by rotating the base part in one direction about the center axis, the workpieces are polished while sequentially moving the workpiece holding units that hold the workpieces to the plurality of polishing positions. Consequently, it is possible to change the polishing area or the polish conditions of the workpiece at each polishing position by, for example, changing each workpiece polishing unit. As a result, it is possible to manufacture an accurate workpiece to flexibly meet various outer shape specifications.

Furthermore, the workpiece polishing unit is not provided at the workpiece exchange position, so that it is possible to easily exchange the polished workpiece with the workpiece that is not yet polished while polishing each workpiece at each polishing position. Consequently, it is not necessary to stop the polishing device to exchange the workpiece, and it is possible to substantially improve productivity and operability compared to the conventional polishing device.

The present invention polishes the workpieces while sequentially moving the workpiece holding units that hold the workpieces to the plurality of polishing positions, so that it is possible to manufacture accurate workpieces to flexibly meet various outer shape specifications. Furthermore, it is possible to easily exchange the polished workpiece with the workpiece that is not yet polished at the workpiece exchange position while polishing each workpiece at each polishing position, so that it is possible to improve productivity and operability compared to the conventional polishing device.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic view illustrating a schematic configuration of a polishing device according to an embodiment of the present invention:

FIG. 2 is a plan view schematically illustrating main parts of a base part and a rotation driving unit in the polishing device according to the embodiment of the present invention;

FIG. 3 is a bottom view schematically illustrating the main parts on a bottom surface side of the base part, and the rotation driving unit in the polishing device according to the embodiment of the present invention:

FIG. 4A is a perspective view schematically illustrating a workpiece holding unit that can hold a machining target lens:

FIG. 4B is a bottom view illustrating a lower end part of the workpiece holding unit:

FIG. 5 is a cross-sectional perspective view illustrating that a machining target lens held by the workpiece holding unit is polished by a workpiece polishing unit in the polishing device according to the embodiment of the present invention; and

FIG. 6 is a plan view illustrating a schematic configuration of a polishing surface of a polishing tool in the polishing device according to the embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(Polishing Device)

The polishing device according to the embodiment of the present invention will be described below with reference to FIGS. 1 to 6 . Note that parts that are unnecessary for explanation will be omitted, and some parts are illustrated by being enlarged or reduced for ease of explanation.

A polishing device 1 according to the present embodiment is a device that polishes and machines a machining target surface (polishing target surface) of a workpiece such as an optical lens.

As illustrated in FIG. 1 , the polishing device 1 includes a base part 10, a plurality of workpiece holding units 20 that hold machining target lenses (workpieces) 4, a plurality of workpiece polishing units 30 that polish the machining target lenses 4, a driving pulley 40, a polishing liquid storage unit 50, and a control unit 60. FIG. 1 is a schematic view illustrating a schematic configuration of the polishing device 1 according to the present embodiment.

The base part 10 is pivotally supported by a shaft part 3 on abase 2. The base part 10 is provided on the shaft part 3 rotatably about a center axis (shaft part 3) of the base pail 10.

The base part 10 includes a table 11 whose entire shape in plan view is a substantially circular shape. At an outer circumferential edge of the table 11, an outer wall part 12 is provided to stand in a vertical direction with respect to the table 11 of the base part 10. Thus, the base part 10 is formed as a circular frame part. The outer wall part 12 is provided, so that it is possible to prevent a polishing liquid used to polish the machining target lens 4 from dropping to surroundings of the base part 10. At an upper part of the outer wall part 12, a base part side scattering prevention part 14 for preventing the polishing liquid from scattering is provided to stand. Furthermore, at a center of the base part 10, a columnar part 13 whose shape in plan view is a substantially circular shape is provided.

In an area partitioned and formed between the outer wall part 12 and the columnar part 13 in the table 11 of the base part 10, six fixing parts 15 that can attachably and detachably fix the workpiece holding units 20 are provided as illustrated in FIG. 2 . Furthermore, each fixing part 15 is arranged mutually at equal intervals on an identical circumference at an arbitrary distance from the center axis of the base part 10. Note that, although a case where the six fixing parts 15 are provided will be described as an example in the present embodiment, the present invention is not limited to the present embodiment. At least the two or more fixing parts 15 only need to be provided. Furthermore, FIG. 2 is a plan view schematically illustrating main parts of the base part 10 of the polishing device 1 and the driving pulley 40. FIG. 2 virtually illustrates polishing positions A to E that are positions at which the machining target lenses 4 are polished, and a workpiece exchange position F that is a position at which the polished machining target lens 4 is exchanged with a machining target lens that is not yet polished.

The fixing part 15 includes at a center part a protrusion part 15 a that protrudes in the vertical direction from the table 11 of the base part 10, and a pair of rotation prevention parts 15 b that protrude from a side circumferential surface of the protrusion part 15 a. The pair of rotation prevention parts 15 b are provided protruding mutually in opposite directions from the protrusion part 15 a. Furthermore, the protrusion part 15 a and the rotation prevention parts 15 b can fit to a lower end part of the workpiece holding unit 20. The fixing parts 15 may be provided on the table 11 rotatably about the center axes of the fixing parts 15. In this case, it is preferable to electrically connect each fixing part 15 to the control unit 60, and control an operation of each fixing part 15 according to an operation command of the control unit 60.

On a back surface side opposite to a side provided with the fixing parts 15 in the table 11 of the base part 10, six driven pulleys 16 are provided meeting installation positions of the fixing parts 15 (workpiece holding units 20) as illustrated in FIG. 3 . FIG. 3 is a bottom view schematically illustrating main parts on a bottom surface side of the base part 10, and the driving pulley 40 of the polishing device 1. An endless belt 41 is wound around outer circumferences of the five driven pulleys 16 of the six driven pulleys 16. These five driven pulleys 16 are at positions meeting the polishing positions A to E. Furthermore, the endless belt 41 is not wound around the driven pulley 16 at a position meeting the workpiece exchange position F. The endless belt 41 is wound around the driving pulley 40, too, and, when the driving pulley 40 rotates, power transmits to the five driven pulleys 16 via the endless belt 41. Consequently, it is possible to rotate and drive the base part 10 on the shaft part 3 in one direction about the center axis of the base part 10.

The workpiece holding unit 20 has a cavity inside as illustrated in FIG. 4A, and can hold the machining target lens 4 of a flat convex shape at an upper end part of the workpiece holding unit 20. FIG. 4A is a perspective view schematically illustrating the workpiece holding unit 20 that can hold the machining target lens 4. The workpiece holding unit 20 includes at an upper end part a placement part 21 that can hold the machining target lens 4 such that a polishing target surface (convex surface) of the machining target lens 4 is exposed. A placement surface 21 a of the placement part 21 is provided with a difference in height such that a height position becomes lower than a periphery part 21 b. Consequently, the machining target lens 4 can be fitted to and placed on the placement part 21. Furthermore, part of the periphery part 21 b is provided with a cutout part 24. The cutout part 24 linearly extends over an arbitrary distance toward a direction of a lower end part of a sidewall part 25 of the workpiece holding unit 20. Consequently, it is possible to expand a diameter of the periphery part 21 b according to a size of the machining target lens 4 when fitting and placing the machining target lens 4 onto the placement part 21. Furthermore, the sidewall part 25 of the workpiece holding unit 20 is provided with a pair of through-holes 26 that penetrate the workpiece holding unit 20. By, for example, causing a bolt to penetrate the sidewall part 25 through the pair of through holes 26, and tightening the penetrating bolt by a nut from an opposite side, it is possible to reduce the diameter of the periphery part 21 b. Consequently, it is possible to fix the machining target lens 4 at the periphery part 21 b, and prevent the machining target lens 4 from being detached from the placement part 21.

Furthermore, as illustrated in FIG. 4B, the lower end part of the workpiece holding unit 20 is provided with an insertion part 22 that allows insertion of the protrusion part 15 a of the fixing part 15 of the base part 10. FIG. 4B is a bottom view illustrating the lower end part of the workpiece holding unit 20. Furthermore, the lower end part of the workpiece holding unit 20 is provided with a pair of fitting groove parts 23, too, that can fit with the protrusion part 15 a of the fixing part 15. The pair of fitting groove parts 23 continue to the insertion part 22.

The workpiece polishing units 30 are respectively provided at the five polishing positions A to E for polishing the machining target lenses 4 so as to be arranged facing the machining target lenses 4 held by the workpiece holding units 20 (see FIG. 2 ). Furthermore, the workpiece polishing unit 30 is not provided at the workpiece exchange position F for exchanging the polished machining target lens 4 (see FIG. 2 ).

As illustrated in FIGS. 5 and 6 , the workpiece polishing unit 30 includes a polishing tool 31, a driving unit 32, a polishing liquid supply unit 33, and a polishing unit side scattering prevention part 35. FIG. 5 is a cross-sectional perspective view illustrating that the machining target lens 4 held by the workpiece holding unit 20 is polished by the workpiece polishing unit 30. FIG. 6 is a plan view illustrating a schematic configuration of a polishing surface 31 b of the polishing tool 31.

As illustrated in FIGS. 5 and 6 , the polishing tool 31 includes a main body part 31 a, the polishing surface 31 b, a female screw part 31 c, and polishing liquid supply holes 31 d. Aside of the main body part 31 a that faces the machining target lens 4 is provided with the polishing surface 31 b for polishing the machining target lens 4. The polishing surface 31 b has a shape that is a substantially concave shape, and can come into planar contact with, press and polish a polishing target surface of the machining target lens 4. The polishing surface 31 b is formed by a polishing pad such as polyurethane. In this case, the shape of the polishing surface 31 b is not limited to the substantially concave shape, and can be appropriately changed according to the shape and polishing conditions of a machining target lens. Furthermore, the polishing surface 31 b is not limited to the polishing pad, and a whetstone, a pellet and the like may be used.

A side of the main body part 31 a opposite to the side that faces the machining target lens 4 is provided with the female screw part 31 c. The female screw part 31 c is screwed with a male screw part of a connection part 32 a described later. Thus, the polishing tool 31 is coupled to the driving unit 32.

The main body part 31 a and the polishing surface 31 b are provided with the three polishing liquid supply holes 31 d for supplying the polishing liquid to the polishing surface 31 b. Furthermore, in the polishing surface 31 b, discharge paths 31 e that continue to the polishing liquid supply holes 31 d extend toward the periphery part of the polishing surface 31 b. Consequently, it is possible to discharge the polishing liquid supplied from each polishing liquid supply hole 31 d through the discharge path 31 e. Note that at least the one polishing liquid supply holes 31 d and the one discharge paths 31 e only need to be provided to the main body part 31 a and the polishing surface 31 b in the present invention. The numbers of the polishing liquid supply holes 31 d and the discharge paths 31 e are not limited in particular.

The driving unit 32 can rotate the polishing tool 31 connected with the connection part 32 a about an axial center of the polishing tool 31. Furthermore, the <hiving unit 32 presses the polishing tool 31 against the machining target lens 4 such that the polishing surface 31 b of the polishing tool 31 comes into pressure contact with (abuts on) the polishing target surface of the machining target lens 4 to polish. The driving unit 32 is electrically connected with the control unit 60, and an operation of the driving unit 32 is controlled according to an operation command of the control unit 60.

The polishing liquid supply unit 33 supplies the polishing liquid supplied from the polishing liquid storage unit 50 to a space between the polishing surface 31 b of the polishing tool 31 and the polishing target surface of the machining target lens 4. When the polishing tool 31 is rotated to polish the machining target lens 4, the polishing liquid supply unit 33 preferably does not continue to the polishing liquid supply holes 31 d. On the other hand, when only the workpiece holding units 20 are rotated to polish the machining target lenses 4, the polishing liquid supply unit 33 may continue to the polishing liquid supply holes 31 d.

The polishing unit side scattering prevention part 35 shields surrounding of the polishing tool 31 as illustrated in FIG. 5 . The polishing unit side scattering prevention part 35 hangs down to at least the polishing position of the polishing tool 31 for the machining target lens 4. Consequently, it is possible to prevent the polishing liquid from scattering to the surroundings while the polishing tool 31 polishes the machining target lens 4.

Note that, when polishing the machining target lens 4, the workpiece polishing unit 30 can incline the polishing tool 31 at an arbitrary angle with respect to the machining target lens 4 to polish. Consequently, it is possible to appropriately adjust a polishing area of the polishing target surface of the machining target lens 4. As a result, although it is difficult to polish a top part of the machining target lens 4 when the polishing tool 31 abuts on the machining target lens 4 from the vertical direction, it is possible to easily polish the top part by making the polishing tool 31 abut on the machining target lens 4 in a state where the polishing tool 31 is inclined at an arbitrary angle with respect to the vertical direction.

As described above, the driving pulley 40 is coupled to the five driven pulleys 16 provided on a back surface side of the table 11 of the base part 10 with the endless belt 41 interposed therebetween. The driven pulleys 16 are electrically connected with the control unit 60, and operations of the driven pulleys 16 are controlled according to an operation command of the control unit 60. Note that the driving pulley 40 may be configured to be directly coupled to the base part 10 with the endless belt 41 interposed therebetween. In this case, the endless belt 41 is preferably wound around an outer circumference of the base part 10. Even in this case, when the driving pulley 40 rotates, power transmits to the base part 10 through the endless belt 41, it is possible to rotate and drive the base part 10 on the shaft part 3 in one direction about the center axis of the base part 10.

The polishing liquid storage unit 50 stores the polishing liquid inside. The polishing liquid storage unit 50 is connected with a plurality of supply pipes 51 for supplying the polishing liquid to each workpiece polishing unit 30. Furthermore, an on-off valve 52 is provided to a middle of a route of each supply pipe 51. Opening and closing the on-off valve 52 may be controlled by, for example, the control unit 60. In this case, when the on-off valve 52 is opened according to an operation command of the control unit 60, the polishing liquid is pumped to each workpiece polishing unit 30 through the supply pipe 51.

The control unit 60 is electrically connected with each part of the polishing device 1, and integrally or partially controls the operation of the polishing device 1. For example, the control unit 60 can control an operation of each part of the workpiece polishing units 30, the on-off valves 52, the workpiece holding units 20 and the like. In this regard, the control unit 60 can be configured as, for example, a computer that includes an arithmetic operation unit and a storage unit. The storage unit stores polishing conditions and driving conditions of the driving pulley 40 in advance. Examples of the polishing conditions include a rotational speed of the polishing tool 31 of the workpiece polishing unit 30, a polishing time, and a polishing area of a polishing target surface. Furthermore, in a case where each workpiece holding unit 20 is rotated, examples of the polishing conditions include a rotational speed and a rotation (polishing) time of each workpiece holding unit 20. Furthermore, examples of the driving conditions of the driving pulley 40 include a driving time of the driving pulley 40 and the like matching the rotational speed and the polishing time of the driving pulley 40.

(Polishing Method)

Next, a method for polishing a machining target lens by using the polishing device 1 according to the present embodiment will be described below.

First, the workpiece holding unit 20 that holds the machining target lens that is not yet polished is fixed to the fixing part 15 at the workpiece exchange position F. Furthermore, the control unit 60 performs operation control to rotate and drive the driving pulley 40. Thus, the table 11 of the base part 10 rotates in a direction indicated by an arrow X in FIG. 2 , and the workpiece holding unit 20 fixed to the fixing part 15 at the workpiece exchange position F is conveyed to the polishing position A.

When the workpiece holding unit 20 is conveyed to the polishing position A, the machining target lens that is not yet polished is polished under predetermined polishing conditions by the workpiece polishing unit 30 provided at the polishing position A. The control unit 60 performs operation control to cause the workpiece polishing unit 30 to perform polishing. Furthermore, while the polishing position A is polished, a new machining target lens that is not yet polished is replenished at the workpiece exchange position F. That is, the workpiece holding unit 20 that holds the new machining target lens that is not yet polished is fixed to the fixing part 15 at the workpiece exchange position F.

When polishing ends at the polishing position A. and replenishment of the new machining target lens that is not yet polished ends at the workpiece exchange position F, the control unit 60 performs operation control to rotate and drive the driving pulley 40 again. Thus, the table 11 of the base part 10 rotates again in the direction indicated by the arrow X, and the machining target lens polished at the polishing position A is conveyed to the polishing position B while being held by the workpiece holding unit 20. Subsequently, the machining target lens is polished under the predetermined polishing conditions by the workpiece polishing unit 30 provided at the polishing position B. Furthermore, the new machining target lens that is not yet polished and is replenished at the workpiece exchange position F is conveyed to the polishing position A. Furthermore, the new machining target lens that is not yet polished is polished under the predetermined polishing conditions by the workpiece polishing unit 30 provided at the polishing position A.

Thus, the machining target lens that is not yet polished and is replenished at the workpiece exchange position F is sequentially conveyed from the polishing position A to the polishing position E by intermittent rotation of the table 11 of the base part 10. Furthermore, the machining target lens is polished under the predetermined polishing conditions by each workpiece polishing unit 30 installed at each of the polishing positions A to E. When whole polishing ends at the polishing positions A to E. and the machining target lens returns to the workpiece exchange position F again, the polished machining target lens is exchanged with the machining target lens that is not yet polished at the workpiece exchange position F.

As described above, according to the polishing method that uses the polishing device 1 according to the present embodiment, by, for example, varying the polishing conditions at each of the polishing positions A to E and varying each installed workpiece polishing unit 30, it is possible to manufacture an accurate lens to flexibly meet various outer shape specifications. Furthermore, it is possible to exchange a polished machining target lens with a machining target lens that is not yet polished while polishing each machining target lens at each of the polishing positions A to E, and it is not necessary to stop the polishing device 1 to exchange the machining target lenses. Consequently, it is possible to substantially improve productivity and operability compared to the conventional polishing device. 

1. A polishing device that polishes a workpiece, the polishing device comprising: a plurality of workpiece holding units that respectively hold the workpieces; a base part that is rotatable about a center axis, and is arranged such that the plurality of workpiece holding units are arranged mutually at an equal interval on an identical circumference at an arbitrary distance from the center axis; and a plurality of workpiece polishing units that polish polishing target surfaces of the workpieces held by the workpiece holding units, wherein the plurality of workpiece polishing units are provided above the base part and at a plurality of polishing positions for polishing the workpieces, and are not provided at a workpiece exchange position for exchanging the polished workpieces held by the workpiece holding units, the plurality of polishing positions and the workpiece exchange position are provided on an identical circumference about the center axis of the base part, and the base part rotates in one direction about the center axis to sequentially move the workpiece holding units that hold the workpieces to the plurality of polishing positions such that the plurality of workpiece polishing units polish the workpieces, and moves the workpieces polished by the plurality of workpiece polishing units to the workpiece exchange position, and exchanges the polished workpieces with a workpiece that is not yet polished.
 2. The polishing device according to claim 1, wherein the workpiece holding units are attachably and detachably provided on the base part.
 3. The polishing device according to claim 1 further comprising: a plurality of driven pulleys that are provided to the base part and are respectively provided to meet the plurality of workpiece holding units; an endless belt that is wound around all driven pulleys at positions meeting the polishing positions among the plurality of drive pulleys, or an outer circumference of the base part; and a driving pulley that is coupled to all the driven pulleys at the positions meeting the polishing positions or the base part with the endless belt interposed therebetween.
 4. A polishing method for polishing the workpiece by using the polishing device according to claim 1, the polishing method comprising: causing the plurality of workpiece holding units to respectively hold the workpieces, the plurality of workpiece holding units being arranged mutually at an equal interval on an identical circumference at an arbitrary distance from the center axis of the base part: rotating the base part in one direction about the center axis to sequentially move the workpiece holding units that hold the workpieces to the plurality of polishing positions such that the plurality of workpiece polishing units polish the workpieces; and moving the workpieces to the workpiece exchange position, and exchanging the polished workpieces with a workpiece that is not yet polished. 